Continuity mistake: When the crook kicks the door on a building in the fake town it falls over, but the same building falls over again when the dynamite goes off.
Continuity mistake: When Mongo first comes into town and the man on the horse says "You can't park that animal here," Mongo punches the horse and its rider, and the horse falls. Before the cut to the close up of the man (obviously the stunt double), his head is facing toward the horse's head. After the cut to the close up of the man, his body is facing the opposite direction.
Continuity mistake: After Mongo punches the horse and it's down, the snout is pointed toward the chest. In the close up, the head is at a more natural angle.
Continuity mistake: When the Sheriff comes into Lili's dressing room, she has her left hand resting on the desk.When she takes the rose you can tell her left arm is down to her side now. When she tells the sheriff to have a seat, she only raises her right arm but in the next shot her left arm is raised with her hand in the desk again.
Continuity mistake: When Mongo gets the "candygram", he closes his eyes BEFORE it explodes in his face. True, that is necessary for safety, but if he would have tilted his head just a little more, his hat would have blocked the view of his eyes.
Continuity mistake: The scene where the gang stampedes through Rockridge, a thug on horseback lassos a man who is dragged down with the rope slipping down around his feet. As he's dragged foot first through the mud, he says "Well, that's the end of this suit" only now, the rope is up around his chest and under his arms and he's being pulled in a head first direction.